This invention relates to a tool for bending wire to form a controlled bend in it, and more particularly to a tool for bending electrical wires.
Electrical wires are typically in the form of a cylinder of indeterminate length, and encased within an insulating sheath. The electrical wire may be a single strand, or may be a plurality of strands twisted in helical fashion to form an approximately cylindrical configuration. These wires are of various diameters, materials, and stiffness. In use, a portion of the insulation, at an end of the wire, is removed, and the bare wire is then formed into a controlled bend. The controlled bend has an arcuate portion or bight with a relatively straight portion or leg at each end. It is desirable that the two legs be parallel, or approximately parallel, for ease of assembly to a contact. Typically, the contact is a screw having a threaded shaft and a slotted head of substantially larger diameter than the shaft, the controlled bend being placed so that the two legs straddle the threaded shaft of the screw, and are beneath the head of the screw. After positioning the controlled bend of the wire in this manner, the screw is tightened, so that the underside of the head of the screw engages the electrical wire controlled bend and presses it against another part of the contact structure.
To form the controlled bend in the electrical wire, pliers are typically used, the workman grasping one end portion of a generally straight wire, without insulation on the end portion, and bends the wire to form a controlled bend. Care and skill are required to form the controlled bend in the wire so that the legs are in the desired relation to each other. If the leg at the free end of the wire is not bent far enough, that is, is bent through significantly less than 180.degree., there will result a bend which is of an open V-shape, which provides a structure which might be too large to be positioned in the terminal structure, due to parts providing a limited space for the bent wire. When this occurs, time is consumed in rebending the wire with the intent of making the two legs substantially parallel, but care must be taken to avoid bending the leg forming the free end of the wire too much for, in that event, the leg forming the free end of the wire will substantially close the opening which is used for the straddling of the screw shank by the two legs of the bent wire. Also, if too much force is initially applied to the wires, a closed loop will be formed, prohibiting manipulation of the wire so as to straddle the screw shank.
In addition to pliers, there have been provided various wire bending tools for use in bending electrical wires, and other wires, an example of which is Bacon U.S. Pat. No. 3,253,286, in which there is a loop forming tool having a screwdriver with a handle and a shank, and a blade extending generally parallel to, but located radially outwardly of, the shank. An end of a wire is placed between the shank and the blade, and the screwdriver is rotated to form a substantially closed loop in the end of the wire. The amount that the wire is bent, and therefore the relationship of the legs of the bend, is dependent upon the skill and strength of the workman, and the stiffness of the wire, so that bends of the desired configuration are not readily obtainable.
Sibley U.S. Pat. No. 789,941, Frank U.S. Pat. No. 2,430,119, and Sullivan U.S. Pat. No. 3,095,912 provide screwdrivers with an axially extending tang adjacent to the blade of the screwdriver, the tang engaging an end portion of a wire and bending it around a screw as the screwdriver blade engages the slot in the screw head, thereby tightening the screw and forming a bend in the wire.
Windsor U.S. Pat. No. 4,751,840 provides a tool for making bends in a wire comprising a tool having a shaft with a square drive-end engaged in a mandrel having two pins spaced from each other and parallel to the axis of the shaft, for bending wire approximately 90.degree..
Wingert U.S. Pat. No. 4,257,159 provides a wire bending tool including a handle having a shank extending from it in which there is a radially extending hole. An end of a wire is inserted into the hole, and the wire is rotated around the shank to partly form a loop, the extent of the radius of the bend being determined by the diameter of the shank, and therefore not being suitable for a variety of thicknesses of wire.
Yadon U.S. Pat. No. 2,326,090 provides a terminal connector which comprises a disc with a hole, through which the shank of a terminal screw is passed. The disc has a pair of upstanding flanges, which are spaced apart. A wire is passed adjacent the shank of the screw, and between the spaced flanges, after which a screwdriver is used to rotate the screw and the washer to bend the wire about the screw shank.
Poliak et al U.S. Pat. No. 4,060,305 provides a terminal construction having as a part of it a loop forming tool. The tool portion comprises a solid base having a stepped cavity extending into it, the base being formed adjacent to the cavity with a rounded shoulder which is tangent to the cavity and to an outer wall of the base. The end of a wire is inserted into the cavity, and the wire is bent around the shoulder until it engages the side of the device; the wire is then placed on a screw forming part of the wire terminal.
The tools of Sibley, Frank, Windsor and Yadon have the same deficiencies as noted above in connection with Bacon. Consequently, these tools are not able to form controlled bends in a consistent and conventional manner, and cannot provide a controlled bend in which the legs are substantially parallel. With all of these tools, great care is required in order to achieve the formation of a bend of optimum configuration for placing on the threaded shank of a terminal screw. Poliak et al is a combined terminal and tool device, and is not a separate, readily used workman's tool for making controlled bends in wires in preparation for placement of the wires on electrical terminal screws separate from the tool.